Correct MAC revision bits. Previously it always cleared bit 20 and
bit 21.
Add preliminary support for RTL8106E PCIe FastEthernet.

H/W donated by:	RealTek Semiconductor Corp.
MFprojects/camlock r256619:
Restore BIO_UNMAPPED and BIO_TRANSIENT_MAPPING in biodonne() when unmapping
temporary mapped buffer.  That fixes double unmap if biodone() called twice
for the same BIO (but with different done methods).

Move mapping removal before calling bio_done() method.  I believe that it is
very wrong to do anything to BIO after reporting completion.  kib@ thinks
it was done for some forgotten now case when bio_done() method needed mapped
buffer. But 1) if BIO was sent as unmapped, then IMO done() should be called
in the same way; 2) IMO there is no guatantee that buffer will be mapped at
this point at all, for example, if all underlying stack supports unmapped
I/O, so bio_done() handler can not expect that.